1. Field of the Invention
This invention relates to apparatus and methods for measuring forward flow and backflow in a conduit, such as the backflow (or forward flow) of water in an irrigation pipe, and controlling or shutting down the flow on the occurrence of significant backflow (or forward flow).
2. Background Art
Systems for measuring flow through a conduit have a long history and so a number of general types of systems for measuring flow have, thus, naturally developed. The size of the conduit being used, accuracy, cost, and other factors all play a role in determining what specific device will be used for a given application.
One type of flow measurement system is the pressure differential system which works on the principle that when the flow in a conduit is in some way restricted, kinetic energy increases at the expense of available potential energy. The pressure differential system utilizes some method of restricting the flow in the conduit and the resulting pressure difference is measured and the flow rate calculated, using a known equation, fixed parameters of the system, and the pressure differential measured.
The desire to measure flow through a conduit arises in a number of different ways. The need to control the amount of fluid/material delivered, the time over which the fluid/material is delivered, the need to stop delivery on the happening of a predetermined condition or conditions, and the desire to measure and track the amount of fluid/material delivered are among these.
In regard to the desire to stop or control delivery on the happening of a predetermined condition or conditions, it is often the case that certain conditions will indicate a malfunction in the system. If a malfunction has occurred or is occurring, shutting down the system may be required to avoid damage throughout the system.
One such condition is the occurrence of backflow. For example, in is an agricultural irrigation system, the presence of backflow may indicate inadequate pressure or water source, and this may result in damage to the flow measurement equipment or other equipment associated with the system. Pumps are often particularly susceptible to damage if operated "dry".
In agricultural irrigations systems, the irrigation water source may suddenly be cut off for any number of reasons, or the flow may be substantially reduced. In such a case, although the irrigation pump would continue to operate, little or no additional water would enter the system. The resulting lack of pressure in the system could result in backflow. If backflow were detected, the system could be shut down. This would reduce the likelihood of damage to the pump supplying the system, the flow measurement apparatus, or other associated equipment, and reduce the possibility of well contamination from fertilizers, insecticides, etc.
The typical system, unfortunately, is designed to measure flow through the conduit in one direction only, usually the direction of intended flow. In such a system, no apparatus for measuring backflow is available and thus any data relating to backflow is ignored. (In fact, very slow flow oftentimes cannot be measured.) Other systems may measure flow generally, without regard to direction. In these systems backflow may be being measured but there is no way for a user or control system to discern this and the system takes no action based on backflow. Since no provisions for measuring or reacting to backflow are incorporated in such systems, damage or disablement of the system may result if sufficient backflow occurs. Additionally, the cause of the backflow may itself damage the system.
It would therefore be an advantage to provide a system for measuring fluid flow (including both single-phase and multi-phase) in a conduit which is also adapted for measuring backflow and, if desired, taking action based on the occurrence of backflow.